This invention relates to a high voltage operational amplifier, and more particularly to a high-output voltage amplifier in which the input stage and output stage are electrically separated.
An typical operational amplifier amplifies a voltage difference on the inputs to generate a desired output voltage. If the desired output voltage exceeds 50 V, the design of the amplifier typically cascades multiple transistors to reach the required control voltage for the output stage. This design leads to increased signal propagation times and results in intermodular distortions. In case of thermal overload or other component failure like the breakdown of a junction, a voltage breakdown between the input stage and output stage can occur, jeopardizing the low-voltage circuitry.
Thus the aim of this invention is to present a circuit design for the control of high voltages which will have short response times to the change of an input signal as well as providing effective electrical separation between the input and output circuitry.
This invention relates to a high voltage operational amplifier in which the output stage is formed from one or two current sources controlled by opto-electronical means. The linearity of the output stage is achieved by means of a feedback loop. If the target output voltage is independent of the high voltage output, e.g. by means of generating the low-voltage feedback by means of a mechanical sensor, then this high voltage operational amplifier can be used as an isolation amplifier.
This invention allows the production of high voltage amplifiers for different voltage and current ranges with largely unchanged internal layout. The circuit as described by this invention is proof against short circuiting and guarantees, by merit of the electrical separation of input and output, the highest possible protection of circuitry connected to the input stage. This invention is suitable for mirror focusing controls, piezo controls, high-voltage power supplies, etc.